Rescattering Effect and Near Threshold Enhancement of $p\bar p$ System

TL;DR

This paper explains the near-threshold enhancement of the proton-antiproton system observed in certain particle decays using a quantum field theory approach focusing on rescattering effects, particularly pion exchange.

Contribution

It introduces a simple quantum field theory method to account for final state interactions, emphasizing the dominant role of rescattering via pion exchange in the observed enhancement.

Findings

Rescattering effects can explain the near-threshold enhancement.

Pion exchange rescattering is the dominant interaction.

Results align well with experimental observations.

Abstract

We study the observed enhancement of a $p\bar p$ system near the threshold in the process $J/\psi \to \gamma p\bar p$ and $e^+ e^- \to p\bar p$. From early studies the enhancement can be explained by final state interactions, which are in general taken into account with some potential models. In this work we offer a simple approach within quantum field theory to explain the observed enhancement. We point out that among different final state interactions the rescattering in a $N\bar N$ system though exchange of $\pi$ is the most important. The effects of the rescattering is completely fixed by the well-known coupling $g_{\pi NN}$. Our results show that the enhancement in $J/\psi \to \gamma p\bar p$ and $e^+ e^- \to p\bar p$ can be well described with the rescattering effects.